The embodiment relates to a light emitting device package, a lighting module and a lighting system.
A light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into optical energy. The p-n junction diode can be formed by combining group III elements and group V elements of the periodic table with each other. The LED can represent various colors by adjusting the compositional ratio of compound semiconductors.
When a forward voltage is applied to the LED, electrons at an n layer are combined with holes at a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. This energy is mainly emitted as heat or light, and the LED emits the energy as the light.
A nitride semiconductor represents superior thermal stability and wide band gap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been developed and extensively used.
A white light emitting device (white LED) can be realized by mixing individual R, G, B light sources with each other, or converting a phosphor through a pump beam of a UV light or a blue light. The scheme of converting the phosphor has advantages in terms of the manufacturing cost, the adjustment of a color temperature, and light emission efficiency.
Meanwhile, when the white LED is realized by utilizing the phosphor, a portion of a blue light or a UV light serving as a matrix is not absorbed into the phosphor, but extracted to the outside, and a remaining portion of the blue light or the UV light is combined with the phosphor to create a color light having a wavelength longer than that of the light of the matrix. When the extracted light and the color light are mixed with each other, white LEDs representing various color temperatures are realized according to the mixed ratios between the two lights.
However, according to the related art, when an encapsulant mixed with a phosphor is applied or a package including an encapsulant surrounding the phosphor is employed, a portion of a created light may be re-introduced into a chip due to the refractive index contrast between the encapsulant and air that is a medium observed at the final stage.
In addition, according to the related art, since a light converted by the phosphor creates a light having an omnidirectional characteristic in a spontaneous emission process, a portion of the light cannot but be re-introduced into the chip.
Therefore, according to the related art, if a light is re-introduced into the chip, light emission efficiency may be reduced due to light loss caused by the light absorption in the chip. In addition, the reliability for the chip may be degraded. Accordingly, a package to prevent a light from being re-introduced into the chip has to be designed.